Upper looper mechanisms in overlock sewing machine to solve the problem of soiling of cloth by upward scattering of lubricating oil sticking to the upper looper holder when the upper looper holder ascends and descends, are known. In one of such known mechanisms, an O-ring is provided in an upper looper holder guide in which an upper looper slidably penetrates, the upper looper holder passes through the O-ring, and the lubricating oil sticking to the upper looper holder is scraped off by the O-ring when the upper looper holder ascends and descends, so that the lubricating oil may not scatter above from the upper looper holder guide (for example, Japanese Laid-open Utility Model No. H3-30975).
In other upper looper mechanism, the lubricating oil sticking to the upper looper holder is scraped off by the upper end of the through-hole in the upper looper holder guide when the upper looper holder ascends and descends, and by the action of gravity of the lubricating oil itself, the negative pressure induced in a circular oil groove at the outside of the upper looper holder due to rotary motion of the upper looper holder guide, and the action of centrifugal force by rotation of upper looper holder guide, the lubricating oil is attracted into the circular oil groove and is collected in a lower inner part of the sewing machine frame by way of an oil relief hole (for example, Japanese Laid-open Patent No. H9-66184).
As feeding means of lubricating oil into necessary parts such as upper looper mechanism and needle bar mechanism of an overlock sewing machine, a trochoid pump is widely used. For example, an inter lock stitch machine such as a cylinder bed sewing machine employs a two-layer type trochoid pump consisting of a first pump body and a second pump body driven by a pump shaft cooperating with a sewing machine main shaft and linked vertically each other, and in this lubricating oil feeding and discharging device, the lubricating oil collected in an oil pan provided beneath the sewing machine bed is sucked into the first pump body, and is supplied into necessary mechanical parts such as needle bar mechanism and looper mechanism in the sewing machine, and the lubricating oil left over in the bed or arm upper jaw is sucked and collected by the second pump body (for example, Japanese Utility Model Publication No. H3-31272).
However, in the upper looper mechanism disclosed in Japanese Laid-open Utility Model No. H3-30975, the upper looper holder guide is complicated in structure in order to install the O-ring, so that the cost is high. In addition, the O-ring becomes worn by vertical motion of the upper looper holder, and when replacing the worn O-ring, peripheral members must be dismounted including the upper looper holder guide, and the replacement work takes much time and toil.
In the upper looper mechanism disclosed in Japanese Laid-open Patent No. H9-66184, such problem does not exist because O-ring is not used, but the lubricating oil scraped off by the upper edge of the through-hole of the upper looper holder guide cannot be collected sufficiently only the its own gravity or the negative pressure in the circular oil groove induced by rotation of the upper looper holder and the action of rotary centrifugal force. As a result, the residual portion of the lubricating oil is left over around the upper edge of the through-hole and the remaining lubricating oil may scatter upward by the vertical motion of the upper looper holder to soil the thread or cloth.
It is hence the first object of the invention to present an oil discharge device provided in an upper looper mechanism of an overlock sewing machine capable of completely solving the problem of soiling of thread or cloth due to scattering of lubricating oil above the upper looper holder when the upper looper holder ascends and descends, and it is the second object thereof to present an oil discharge device of upper looper mechanism of a compact trochoid pump design as a oil feeding and discharging device for collecting and supplying the lubricating oil, in addition to the first object.